The New Sucking Model and Tongue-Tie

What is the tongue doing when a baby is breastfeeding? Barbara summarises the new sucking model with reference to tongue-tie.

Recently, the Human Lactation Research Group at the University of Western Australia (that includes 3 renowned Professors: Hartmann, Geddes, & Douglas) reviewed ultrasound images from prior research to try to better understand the biomechanics of infant suck during breastfeeding, examining what the tongue is doing. Previously, in 2008, they’d pictured the tongue using a stripping action to extract milk, with a peristaltic wave-like movement drawing the milk out of the breast. (If you’ve attended any talks on tongue-tie or read any books or papers, you’ll be sure to have seen this ultrasound examination referred to in support for cutting ties). This time, however, the researchers discovered that the tongue actually has quite a different role to play. What they now say is that peristalsis is a sequential contraction and dilation of tubular muscle, so wasn’t appropriately applied as a concept in the sucking model.

So what is happening during breastfeeding if the previous model was wrong? Douglas and Geddes’ 2018 paper with the new interpretation was published in the journal Midwifery just recently in March and has proved to be quite contentious. Other experts describe what they see differently, so you can take your pick of hypotheses. I might plump for this one.

Summary of the 2018 paper

The tip of the tongue rests at the level of the lower gum ridge and does not protrude any further during effective seal and sucking. The tongue does not actively grasp or apply itself to the breast. The tongue is a supple organ that as a moist warm cushion activates the milk ejection reflex. It is not independent movement of the tongue that creates the vacuum in the mouth. As the tongue drops with the lower jaw, more breast tissue is drawn into the mouth. Depression of the lower jaw is what generates the vacuum. The tongue’s capacity to move with the lower jaw is not affected by the frenum. The tongue moves only a matter of millimetres! Consequently, a tethering of the tongue is irrelevant. The tongue does not move laterally during the suck cycle, and effective sucking does not require the tongue to lift independently. The upper lip does not need to flange, it just rests in a neutral position for pain-free milk transfer. White flecks previously seen on ultrasound images are not air bubbles at all, they are fat globules.

Others paint a different picture so the disagreement over the tongue’s function illustrates how little clarity there is.

What is not contentious in their paper is what they say about the power of micro movements or tiny adjustments and the need for mothers to experiment a lot with positioning and attachment (fit and hold). There is no getting round the fact that breastfeeding can be a difficult skill to master, particularly following high intervention births when a baby’s willingness and ability to breastfeed may well have been affected by what happens during the birth. But, I digress.

No consensus

It appears that there’s still no consensus amongst lactation consultants on what the role of the tongue is in effective breastfeeding and over explanations for how pain, injury, low milk supply, long and ineffectual feeds, and slow weight gain ‘fit with’ and explain breastfeeding problems with reference to ties.


Douglas, P., & Geddes, D. (2018). The latest practice-based interpretation of ultrasound studies leads the way to more effective clinical support and less pharmaceutical and surgical intervention for breastfeeding infants. Midwifery, 58,145–155. doi:10.1016/j.midw.2017.12.007 (Abandons previous sucking model and adopts one that illustrates tied babies can breastfeed with better positioning and attachment.)

Geddes, D. T., & Sakalidis, V. S. (2016). Ultrasound imaging of breastfeeding—A window to the inside. Journal of Human Lactation, 32(2), 340–349. doi:10.1177/0890334415626152 (Description of the tongue movements during sucking as seen in new ultrasound images.)

Geddes, D. T., Langton, D. B., Gollow, I., Jacobs, L. A., Hartmann, P. E., & Simmer, K. (2008). Frenulotomy for breastfeeding infants with ankyloglossia: Effect on milk removal and sucking mechanism as imaged by ultrasound. PEDIATRICS, 122(1), e188–e194. doi:10.1542/peds.2007-2553 (Nipple compression resolving immediately after frenotomy. Editor’s note: No one has yet established that this is not a result of the short sharp shock of releasing the tongue or, indeed, the power of the mind to bend reality as a result of faith, hope and expectation.)